1. Field of the Invention
The present invention relates to a magnetic ceramic composition and an inductor component using the same.
2. Description of the Related Art
Magnetic ceramic compositions primarily composed of Fe.sub.2 O.sub.3, ZnO, NiO and CuO are known. The magnetic ceramic compositions have been used as magnetic bodies for inductor components as a countermeasure against noise and the like.
Inductor components, such as stacked chip inductors used in personal computers and the like, have low impedance in a high speed signal line at or above 75 MHz as a countermeasure against noise in this signal frequency range. However, in order to eliminate noise in a high frequency range at or above 200 MHz, inductor components must have high impedance and the rise of the impedance curve thereof must be steep.
Hence, magnetic bodies used for the inductor components described above must have low initial permeability .mu..sub.i (for example, below 10) in a high frequency range, such as at or above 200 MHz, and the threshold frequency of this initial permeability .mu..sub.i must be increased at a higher frequency range. In order to decrease deflection and delay of signals, which is specifically required for high speed signals, magnetic bodies used for inductor components must have superior temperature stability.
Conventionally, amounts of ZnO contained in magnetic ceramic compositions were decreased in order to decrease the initial permeability .mu..sub.i. However, even when ZnO is decreased to 0 molar percent, the initial permeability .mu..sub.i is decreased to only 20, and the threshold frequency thereof remains at or below 100 MHz.
In some cases, air-core coils are used for inductor components for high frequency use. In this case, the initial permeability .mu..sub.i is 1. However, the impedance thereof is low in the frequency range of 700 to 800 MHz, and sufficient effects for countermeasures against noise cannot be obtained.
Stacked chip inductors have laminated structures provided with internal conductors therein containing, for example, silver. When sintering is performed to obtain the laminated structure, consideration of suppressing undesired diffusion of components, such as silver, contained in the internal conductors is required. Hence, it is preferable that magnetic ceramic compositions used for magnetic bodies can be sintered at low temperature, such as at or below 930.degree. C.